from collections import defaultdict
A = defaultdict(int)   # 初期値が [] （空リスト）
# https://pcnote.henchoko.com/?p=965

N = int(input())
for i in range(N):
    B = list(map(int, input().split()))
    for j in range(len(B)):
        A[B[j]] += 1

r, s = 0, 0
for key, val in A.items():
    r += val //2
    s += val %2
r += s//4
print(r)